1. Technical Field
The present invention relates to a connector fastening nut and a bolt-nut fastened connector using the same connector fastening nut. The connector fastening nut is fixed to one of two housings and a connector fastening bolt is fixed to the other of the housings so that the two electric connector housings can be engaged with or disengaged from each other more smoothly by use of the connector fastening bolt and nut.
2. Description of the Related Art
With the advance of the diversification of various electric and electronic appliances mounted on an automotive vehicle, recently the number of poles and thereby the size of the connector to be jointed with wire harness have increased more and more. When the size of the connector increases, since a relatively large connector engaging/disengaging force is inevitably required, a connector whose housings arc engaged with or disengaged from each other by use of a pair of bolt and nut has been proposed. In this bolt-nut fastened connector, a tool (bolt and nut) is previously fixed or mounted on the connector housings. In this bolt-nut fastened connector, however, since an excessive fastening force is easily applied to the two connector housings during engagement thereof, there exists a problem in that the connector housings are easily damaged or broken. Therefore, it is necessary to provide a mechanism for preventing an excessive fastening force from being applied to the two connector housings.
Japanese Published Unexamined (Kokai) Patent Application No. 63-13283 discloses a first example of prior art bolt-nut fastened connector provided with a mechanism for preventing an excessive housing fastening force from being applied to the connector housings. In this prior art example, a fastening bolt having a male threaded portion near an end thereof is rotatably fitted to one of two mated connector housings, and a fastening nut having a female threaded portion is fixed to the other of the two connector housings. When the two connector housings have been full engaged, since the male threaded portion of the fastening bolt is disengaged away from (passed through) the female threaded portion of the fastening nut and thereby the fastening bolt is rotated idle, it is possible to prevent the two connector housings from being fastened excessively. In this first prior art example, however, since an elastic spring is provided to always urge the fastening bolt outward so that the male threaded portion of the fastening bolt can be easily engaged with the female threaded portion the fastening nut when the two connector housings are required to be disengaged from each other. Therefore, there exists a problem in that when the fastening bolt is kept rotated even after the male threaded portion of the fastening bolt has passed through the female threaded portion of the fastening nut, the female threaded portion of the fastening nut is damaged due to a large frictional force between the two threaded portions of the bolt and the fastening nut.
To overcome this problem, Japanese Published Unexamined (Kokai) Utility Model Application No. 4-21252 discloses a second example of prior art bolt-nut fastened connector provided with a mechanism which can prevent an excessive fastening force from being applied to the two connector housings. In this second prior art example, an elastic spring is provided fixed to the connector housing just under the fastening nut in such a way that only after the male threaded portion of the fastening bolt has passed through the fastening nut, the fastening nut is urged outward by the elastic spring to facilitate the engagement of the two threaded portions of the fastening bolt and the fastening nut when the two connector housings are required to be disengaged from each other. In this case, however, although the female threaded portion of the fastening nut can be prevented from being damaged, since a resin spring holder having the elastic spring must be additionally fixed to the connector housing, an additional part is required, so that the manufacturing cost increases and further the assembly work is rather complicated.
Further, a fastening nut is usually insertion-molded together with the connector housing. In this case, it is necessary to form a locating hole in the connector housing to determine the position of the insertion-molded fastening nut. However, when the fastening nut is directly insertion-molded together with the connector housing, there exists such a problem that chips attached on the fastening nut remains within the connector housing, with the result that the conduction trouble may occur between the connector terminals of the mated connector housings. In addition, since there exists another problem in that since the treated surface of the threaded portion of the fastening nut is peeled off due to the thread engagement, the threaded portion is easily rusted. To overcome this problem, a water-tight structure is usually adopted. For this purpose, an additional cap member must be fitted into the insertion-molding hole of the connector housing to seal the hole water-tightly. As a result, there arises another problem in that the number of parts and thereby the cost of the bolt-nut fastened connector increase and further the productivity is lowered in the assembly process.